Packaging Film and Method of Manufacture

ABSTRACT

A packaging film having enhanced barrier, sealability, and flex-crack resistance characteristics and is ideal for use in packaging of food products, such as cheese and meat, to increase shelf life thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional patent application Ser. No. 61/653,917 filed May 31, 2012. The aforementioned provisional application is incorporated by reference in its entirety.

BACKGROUND

1. Field

Embodiments of the present inventive concept relate to packaging and, in particularly, to a packaging film having enhanced barrier, sealability, and flex-crack resistance characteristics and is ideal for use with food products, such as cheese and meat, to increase shelf life thereof.

2. Related Art

Flexible packaging, particularly for food, is subject to many demands. The packaging needs to be workable in such a way that the packaging material may be quickly placed around the item to be packaged using machinery. The packaging material must also be of such a quality that it adequately stores the product before the packaging is open. In the case of food products, this typically means that the packaging materials provide an oxygen barrier to maintain freshness.

Ethylene vinyl alcohol (EVOH) is an extrudable resin that has excellent oxygen, flavor, and aroma barrier properties. EVOH resins and packaging materials have been used for several decades as meat and cheese film wrappers and the barrier properties of EVOH with respect to oxygen, grease, oil, flavor additives, and aroma is well understood.

However, when exposed to humidity levels of 85% or higher, the barrier properties of EVOH degrade. To avoid this degradation, the EVOH is typically extruded in a multi-layer symmetrical coextrusion in which specialized tie resins are used to adhere the EVOH to outer polyolefin layers that protect the EVOH from humidity. For example, a three resin, five layer coextrusion of EVOH may include LDPE-Tie Resin-EVOH-Tie Resin-LDPE. In this five layer structure, the LDPE (low density polyethylene) layers protect the EVOH layer from exposure to moisture. Also, the LDPE and Tie Resin are extruded each from one extruder where they are split into two layers and directed to either side of the EVOH layer by a feedblock device. The LDPE and Tie Resin are exactly the same material on both sides of the EVOH, thus it is called a symmetrical coextrusion.

It should be further understood that, when melted, EVOH becomes fluid very quickly with very low melt strength and cannot be extruded as a separate thin film. In extrusion coating, a melt curtain is formed between the exit of the extruder die and the extruder nip. The melt curtain is completely unsupported in this air gap between the die and the extruder nip. Therefore, the melt curtain needs to have enough viscosity and melt strength to keep from tearing apart. Thus, EVOH has traditionally required the above-described five layer structure not only to maintain its barrier properties, but also to provide adjacent structural layers (such as polyethylene) that physically support the coextruded layer of the EVOH. Thus, while EVOH has excellent oxygen barrier properties, EVOH has been considered unsuitable as a barrier layer in some applications for a number of reasons. For one, production of EVOH has required extrusion machines capable of coextruding more than two resins. Such machines are very expensive and not as common as those extruding only two resins. Further, dual tie resin and polyolefin layers are provided on both sides of the EVOH coextrusion to protect the EVOH layer from humidity; however, these multiple layers can increase the material cost of the packaging and increase the thickness of the packaging. This has made EVOH-based packaging less competitive for certain packaging applications.

Accordingly, there is a continuing need for improved and lower cost packaging and a method of making the same that maintains product freshness without presenting cost, processing, or post-use concerns.

SUMMARY

The following brief summary is provided to indicate the nature of the subject matter disclosed herein. While certain aspects of the present inventive concept are described below, the summary is not intended to limit the scope of the present inventive concept. Embodiments of the present inventive concept provide a packaging film and method that does not suffer from the problems and limitations of conventional packaging such as those previously discussed.

Embodiments of the present inventive concept provide a packaging film having enhanced barrier, sealability, and flex-crack resistance characteristics, and is ideal for use with food products, such as cheese and meat, to increase shelf life thereof.

In more detail, embodiments of the present inventive concept provide a packaging film having an innermost sealant layer disposed on a multilayer core structure. The innermost sealant layer and the multilayer core structure may be configured to cooperatively provide a sealant layer comprising a thickness ratio of at least 60% of a total thickness of the packaging film.

The core structure may be co-extruded and may include an outer layer and inner layer on either side of a middle barrier layer. The outer and inner layers may contain a same material. The outer and/or inner layers may contain polyolefins.

The middle barrier layer may contain one of ethylene vinyl alcohol and polyamide.

The packaging film may include an abuse layer disposed on a side of the core structure opposite to the outermost sealant layer. This layer may contain one of biaxially oriented polyethylene terephthalate and nylon.

The packaging film may include an adhesion layer formed within the core structure. The adhesion layer may contain a tie resin and may be formed directly between the inner layer and/or the middle barrier layer.

Embodiments of the present inventive concept may provide a method of manufacturing a packaging film, which may include the step of forming an innermost sealant layer disposed on a multilayer core structure. The innermost sealant layer and the multilayer core structure may be configured to cooperatively provide a sealant layer comprising a thickness ratio of at least 60% of a total thickness of the packaging film. The core structure may be co-extruded and may include an outer layer and inner layer on either side of a middle sealant layer.

The method may include the step of forming an abuse layer on a side of the core structure opposite to the innermost sealant layer. The abuse layer may contain one of biaxially oriented polyethylene terephthalate and nylon.

Additional aspects, advantages, and utilities of the present inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present inventive concept.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present inventive concept are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic illustrating a film with a layer structure, in accordance with first exemplary embodiment of the present inventive concept; and

FIGS. 2 is a schematic illustrating a film with a layer structure, in accordance with second exemplary embodiments of the present inventive concept.

The drawing figures do not limit the present inventive concept to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present inventive concept.

DETAILED DESCRIPTION

Detailed embodiments of the present inventive concept are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present inventive concept in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the present inventive concept.

The terms “a” or “an,” as used herein, are defined as one or more than one. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having” as used herein, are defined as comprising (i.e., open transition). The term “coupled” or “operatively coupled,” as used herein, is defined as indirectly or directly connected.

Turning now to the drawings, and particularly FIGS. 1-2, a packaging film 10 manufactured in accordance with embodiments of the preset inventive concept is illustrated. The packaging film 10 is configured to be utilized to package food products, e.g., cheese and/or meat. The packaging film has enhanced barrier, sealability, and flex-crack resistance characteristics and is particularly ideal for use in packaging the food products and to increase shelf life of the food products relative to conventional packaging. Embodiments of the present inventive concept will be discussed in use with respect to cheese, although it is to be understood that the present inventive concept is equally useable with other food products.

In FIGS. 1-2, two structures of the packaging film 10 are illustrated including:

-   -   (1) PET-LDPE/EVOH/Tie/LDPE-Sealant     -   (2) BON-LDPE/EVOH/Tie/LDPE-Sealant

Each of these structures (1) and (2) for packaging film 10 contains sealant layers that comprise at least 60% of the entirety of the packaging film 20.

As used herein, a “-” is used to indicate layers that are separately formed and attached and “/” is used to indicate layers that are coextruded with one another.

In FIG. 1, the packaging film 10 includes a primary sealant layer 12 formed on an innermost portion of the packaging film 10 relative to a food product 14. The primary sealant layer 12 is made of linear-low-density polyethylene (LLDPE) having a thickness of approximately 1.5 mil. In this manner, the thickness of the primary sealant layer 12 comprises at least a fraction of the thickness of the packaging film 20 in its entirety. It is foreseen that the primary sealant layer 12 may be made of any like material without deviating from the scope of the present inventive concept.

On the primary sealant layer 12 is a multilayer core structure 16 having an inner layer 18, a middle barrier layer 20, and an outer layer 22. The thickness of the core structure 16 is a fraction of the thickness of the packaging film 10 in its entirety, and provides a variety of advantages to the packaging film 10, as discussed herein.

The inner layer 18 is made of low-density polyethylene (LDPE) and has a thickness of a fraction of the thickness of the packaging film 20 in its entirety. It is foreseen, however, that the inner layer 18 may be made of any LDPE material or the like without deviating from the scope of the present inventive concept. The thickness of the inner layer 18 is a fraction of the thickness of the packaging film 10 in its entirety. The inner layer 18 directly abuts the primary sealant layer 12. The layers 12, 18 complement each other by supplementing weaker characteristics of the other. For instance, the inner layer 18 is susceptible to stress cracking in some environments. The primary sealant layer 12, on the other hand, has enhanced seal properties that is significantly higher than that of the inner layer 18.

The middle layer 20 provides an oxygen barrier for the packaging film 10 to the surrounding environment. The middle layer 20 is made of one of ethylene vinyl alcohol (EVOH) or polyamide and has a thickness of a fraction of the thickness of the packaging film 20 in its entirety. It is foreseen, however, that the middle layer 20 may be made of any EVOH or polyamide material or the like without deviating from the scope of the present inventive concept. The thickness of the middle layer 20 is a fraction of the thickness of the packaging film 10 in its entirety.

The outer layer 22 is made of polyolefin and has a thickness of a fraction of the thickness of the packaging film 20 in its entirety. It is foreseen, however, that the outer layer 22 may be made of any polyolefin or the like without deviating from the scope of the present inventive concept. The thickness of the outer layer 22 is a fraction of the thickness of the packaging film 10 in its entirety. The outer layer 22 and the inner layer 18 are made of the same material and sandwich the middle layer 20.

A bonding or adhesion layer 24 is disposed within the core structure 16 during co-extrusion of the layers 18, 20 so that the adhesion layer 24 is in direct connect with and between the inner layer 18 and the middle layer 20, as illustrated in FIG. 1. The adhesion layer 24 is made of one or more specialized tie resins and is operable to increased adhesion between the inner layer 18 and the middle barrier layer 20. In this manner, the inner layer 18 and the middle layer 20 are adhered together. It is foreseen, however, that the adhesion layer 24 may be made of any specialized tie resin(s) without deviating from the scope of the present inventive concept.

On an outermost portion of the packaging film 10 opposite to the primary sealant layer 12 and in non-contact with the food product 14 is an abuse layer 26 to provide a moisture barrier to the packaging film 10. The abuse layer 26 is made of polyethylene terephthalate (PET) and has a thickness of a fraction of the thickness of the packaging film 20 in its entirety. It is foreseen, however, that the abuse layer 26 may be made of any PET material or the like without deviating from the scope of the present inventive concept. For instance, abuse layer 26 of the packaging film 10 illustrated in

FIG. 2 is made of biaxially oriented nylon (BON) instead of PET. The thickness of the abuse layer 26 is a fraction of the thickness of the packaging film 10 in its entirety.

In this manner, the packaging film 10 of the present inventive concept has enhanced barrier, sealability, and flex-crack resistance characteristics. Additionally, the packaging film 10 of the present inventive concept has exceptional seal strength, hot tack, and caulkability. It has been discovered via testing of the packaging film 10 of the present inventive concept that such yields almost zero pin holes in both machine and transverse directions due to the location of layers 12, 14, 16 and low thickness of the abuse layer. Thus, the packaging film 10 is particularly ideal for use with and to store the food product 14, which may be meat and/or cheese, e.g., retail shredded cheese, institutional shredded cheese, chunk cheese, and/or sliced cheese. Although the present inventive concept has been described with reference to the preferred embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the present inventive concept as recited in the claims.

Related patent applications include PCT/US2011/021533 to Knauf and PCT/US2011/021535 to Knauf, the disclosures of which are incorporated herein by reference in their entireties. 

Having thus described the preferred embodiments, the invention is now claimed to be:
 1. A packaging film comprising: an innermost sealant layer disposed on a multilayer core structure, the innermost sealant layer and the multilayer core structure configured to cooperatively provide a sealant layer comprising a thickness ratio of at least 60% of a total thickness of the packaging film.
 2. The packaging film of claim 1, wherein the core structure is co-extruded and includes an outer layer and inner layer on either side of a middle barrier layer.
 3. The packaging film of claim 2, wherein the outer and inner layers contain a same material.
 4. The packaging film of claim 3, wherein the outer and inner layers contain polyolefin.
 5. The packaging film of claim 2, wherein the middle barrier layer contains one of ethylene vinyl alcohol and polyamide.
 6. The packaging film of claim 1, further comprising: an abuse layer disposed on a side of the core structure opposite to the innermost sealant layer.
 7. The packaging film of claim 8, wherein the abuse layer contains one of biaxially oriented polyethylene terephthalate and nylon.
 8. The packaging film of claim 1, further comprising: an adhesion layer formed within the core structure.
 9. The packaging film of claim 10, wherein the adhesion layer contains a tie resin and is formed directly between the inner layer and the middle layer.
 10. A method of manufacturing a packaging film comprising the steps of: forming an innermost layer disposed on a multilayer core structure, the innermost sealant layer and the multilayer core structure configured to cooperatively provide a sealant layer comprising a thickness ratio of at least 60% of a total thickness of the packaging film.
 11. The method of claim 12, wherein the core structure is co-extruded and includes an outer layer and inner layer on either side of a middle sealant layer.
 12. The method of claim 13, wherein the outer and inner layers contain a same material.
 13. The method of claim 14, wherein the outer and inner layers contain polyolefin.
 14. The method of claim 13, wherein the middle sealant layer contains one of ethylene vinyl alcohol and polyamide.
 15. The method of claim 12, further comprising: forming an abuse layer on a side of the core structure opposite to the innermost sealant layer, wherein the abuse layer contains one of biaxially oriented polyethylene terephthalate and nylon.
 16. The method of claim 12, further comprising: adhering the inner layer to the middle barrier layer using an adhesion layer formed within the core structure. 